Can a surface profile tolerance be applied without any datums?

huangyhg

Can a surface profile tolerance be applied without any  datums? I think it probably can but I'd be interested to hear other people's  views.

huangyhg

Norm Crawford • Yes it can. When done so, profile is generally be controlling form only. However, if applied to a closed polygon or surface of revolution without a size tolerance it is also controlling size. If applied to nominally coplanar or colinear features or otherwise multiple irregular features of size, it is controlling location of the features to themselves. The common practice is the control of coplanarity of nominally co-planar surfaces.
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Michael Liu • Graham,

Yes...Based on ASME Y14.5M-1994, a surface profile control applied without a datum reference will control the form of the surface.
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Dennis Schwartz • Yes it can. Norm and Michael gave great explainations.
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Rafael Rivera • Sure you can! There are many applications here are some:

Coplanarity
Profile tolerance can be used for coplanar surfaces to treat two or more surfaces as a single interrupted or non-continues surface. See ASME Y14.5M-1994, page 171, paragraphs 6.5.6 and 6.5.6.1

Conicity
Profile tolerance can be used for conical features as independent control of form. See ASME Y14.5M-1994, page 172, paragraphs 6.5.8

Profile All Over
Profile tolerance can be applied to parts (such as castings) defined by profile tolerances applying “ALL OVER”. See ASME Y14.5M-1994, page 163, paragraphs 6.5.6 and 6.5.2(a)
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Arnold Stiers • Yes, a profile tolerance without datums can be used with basic dimensions to control the form of a feature. However, the lack of datums will not allow the position of this feature to be defined if it's form is part of a functional fit application. It is therefore generally used to control the form or uniformity of a feature as it relates to itself.
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Michael
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Michael Adcock • Most of these response make reference to Y14.5. Did anyone consider that Graham is in the UK and may not be using Y14.5?

Graham, ISO and the related BSI standards also permit profile tolerances to be applied without a datum reference. However the shape of the tolerance zone and applications for a profile tolerance do vary between ISO and ASME. ISO standards and the TC213 committee reject the notion that profile tolerances would be applied to nominally planar surfaces - so don't use profile for coplanar applications. however the standards themselves seem to allow for the exception when using profile tolerances all-around and the all-around profile includes nominally planar surfaces.
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Syed Aatif Nasar • Yes we can , as its is form control
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Nicolas
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Nicolas LEROUGE • I agree with Michael : ISO permits Profile specifications to be applied without datum system. See ISO 1101 (paragraphs 18.5 and 18.7) or even ISO 1660 dedicated to profil tolerance caracteristics with/without datum (this last standard is under evolution at ISO TC213 committee).

But I'd like to put these completary informations relativ to ISO standards (for UK) : ISO doesn't directly prohibit the use of profile symbol on planar surfaces. I think it is more a question of habits. We generally prefear using Position symbol (or flatness symbol when only the form is intended) instead of Profile of any surface symbol on planar surfaces. It's a question of intrinsic caracterics which are assumed to be controled by Profile of any surface symbol, but not by Position symbol: mathematically, there is no intrinsic caracteric for a plane, but there are many for a complex surface ...
That is why ISO standards will never show examples whith Profil symbols for toleranced planes, exept if several planes shoud be taken into account, for instance with 'all arroud' symbol on nominal planar surfaces as Michael said, but also with 'Common Zone' (CZ) modifier on planar surfaces (coplanar or not).
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Jack Cui • form control of single surface is it's basic application.
people above are actually talking about profile tolerancing on plane surfaces.
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S Borlakunta • As per 6.5.4 in ASME Y14.5M-1994, datum is not required for surface profile for cross sections like long extrusions. and as per 6.5.6.1 fig 6-20, not required for co-planar surfaces
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John Miles • Profile can be applied to a contoured surface the same as flatness can be applied to a flat surface. The tolerance zone would be two perfect boundary contours at the specified tolerance in which the produced surface must lie, unrelated to any other feature on the part.
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Ray Admire • Basically a composite to itself!
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Michael Cisneros • While on the issue profile. How do you guys report profile on your inspection report? Perhaps I have some "stinkin thinkin" that needs to be corrected. Let's say you have a profile of 0.5mm relative to datums A, B and C. Your upper control limit worse case is 0.20 and your lower control limit is -0.10. I contend that the reportable profile will calculate out to 0.40mm based on the reading that further deviates ( 0.20mm ) from the baseline and multiplying that reading by 2. Any thoughts?
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Mark Foster • Lots of thoughts, Michael, but that question deserves its own thread. :-)
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Michael
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Michael Adcock • Alot of people continue to chime in with assumptions. No wonder it's difficult to get the field od dimensional engineering & GD&T taken more seriously. Graham has not responded that he's using ASME or ISO. Hate to say it but most of these responses only project what we know "or think we know" onto someone drawing spec. rather than finding out what was specified and working with real knowledge.

P.S. - my earlier comment about ISO not permitting profile tolerances to planar features stands based on an ISO TC213 decission in 2010. With the expection of all around applications, profile tolerances are to be applied to define contoured surfaces and position is to be used to locate and orient planar surface. This descision uphold ISO's current direction for GPS standards. The BSI standards may have modified the use of profile tolerances, but that takes us back to my initial responce. Graham what standard does your drawing specify? If there is no standard then work should be halted before you find yourself in a deep hole with knowone to blame, but yourself.
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Norm Crawford • The question was simply; "Can a surface profile tolerance be applied without any datums?". For both standards, the simple answer is yes.
For the specific context on that answer, as Mark mentioned, the group might benefit more with separate threads on profile with regard to the two most significant standards.